• 전기의세계
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• 제28권10호
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• pp.41-47
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• 1979

The paper develops a method of minimizing power transmission losses by optimum control of reactive power flow. In the past, because the optimizing method considers as the first step the minimization of node voltage deviations and as the second step the minimization of transmission losses within the system, the calculating procedure was more complex and difficult to handle. In this paper, a new computing method for real time control on a digital computer is described which aims at a coordinated use of reactive power sources and voltage regulating devices. The power transmission losses are minimized by a gradient method while satisfying the constrained system voltage conditions and sensitivity parameters are the basis of the method.

• 전기의세계
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• 제29권5호
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• pp.329-335
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• 1980

This paper presents the reliability calculation method in power supply for a part of the power system reliability control. This method involves assuming several systems that can meet the demands, accidents on the transmission facilities and power source and performing the load flow calculation which will lead to the demands which are not served, frequency of the not-served demands and mean value of the not-served demands. In this study the simplified method for reliability calculation by using the maximal flow problem was developed. The results demonstrate the remarkable advantages and more useful than any other methods for the practical applications.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.461-470
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• 2014

This paper presents a probabilistic power flow (PPF) analysis method for distribution network incorporating the randomness and correlation of photovoltaic (PV) generation. Based on the multivariate kernel density estimation theory, the probabilistic model of PV generation is proposed without any assumption of theoretical parametric distribution, which can accurately capture not only the randomness but also the correlation of PV resources at adjacent locations. The PPF method is developed by combining the proposed PV model and Monte Carlo technique to evaluate the influence of the randomness and correlation of PV generation on the performance of distribution networks. The historical power output data of three neighboring PV generators in Oregon, USA, and 34-bus/69-bus radial distribution networks are used to demonstrate the correctness, effectiveness, and application of the proposed PV model and PPF method.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.461-464
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• 2003

A new control volume finite element method is proposed for three dimensional analysis of polymer flow. Tetrahedral finite element is employed and co-located interpolation procedure for pressure and velocity is implemented. Inclusion of pressure gradient term in the velocity shape functions prevents the checkerboard pressure field from being developed. Vectorial nature of pressure gradient is considered in the velocity shape function so that velocity profile in the limit of very small Reynolds number becomes physically meaningful. The proposed method was verified through three dimensional simulation of pipe flow problem for Newtonian and power-law fluid. Calculated pressure and velocity field showed an excellent agreement with analytic solutions for pressure and velocity. Driven-cavity problem, which is reported to yield checkerboard pressure filed when conventional finite element method is applied, could be solved without yielding checkerboard pressure field when the proposed control volume finite element method was applied. The proposed method could be successfully applied to the three dimensional mold filling problem.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.911-914
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• 1998

This paper presents an algorithm that evaluates the transfer capability of composite power systems using probabilistic approaches. The reliability indices calculated by using probabilistic method are expected maximal flow, expected transfer capability margin, and expected power not supplied. In this paper, a successive linear programming technique is used to evaluate transfer capability named maximal flow. Physical constraints considered in the maximal flow problem are the limits of toad voltage, line overloading, and real & reactive power generation. Numerical results on IEEE RTS show that the proposed algorithm is effective and useful.

• 전기학회논문지
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• 제57권11호
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• pp.1954-1961
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• 2008

Microgrid usually consists of a cluster of distributed generators(DGs), energy storage systems and loads, and can operate in the grid-connected mode and the islanded mode. This paper presents detailed descriptions of two different options for controlling the active power of DGs in the microgrid. One is regulating the power injected by the unit to a desired amount(Unit output power control) and the other is to regulate the flow of active power in the feeder where the unit is installed to a constant(Feeder flow control). Frequency-droop characteristics are used to achieve good active power sharing when the microgrid operates in the islanded mode. The change in the frequency and the active power output of DGs are investigated according to the control mode and the configuration of DGs when the microgrid is disconnected from the main grid. From the analysis, this paper proposes a method to determine the droop constant of DGs operating in the feeder flow control mode. Simulation results using the PSCAD/EMTDC are presented to validate the approach, which shows good performance as opposed to the conventional one.

• KIEE International Transactions on Power Engineering
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• 제12A권1호
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• pp.31-35
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• 2002

This paper presents a new operation scheme of UPFC to minimize both generation costs and active power losses in a normal operation state of power system. In a normal operation, cost minimization is a matter of primary concern among operating objectives. This paper considers two kinds of costs, generation costs and transmission losses. The total generation cost of active powers can be minimized by optimal power flow, and active power losses in the transmission system can be also minimized by power flow control of UPFC incorporated with minimization of generation costs. In order to determine amounts of active power reference of each UPFC required for the cost minimization, an iterative optimization algorithm based on the power flow calculation using the decoupled UPFC model is proposed. For verification of the proposed method, intensive studies have been performed on a 3-unit 6-bus system equipped with a UPFC.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.76-85
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• 2016

This paper presents a method of decision on where bus splitting is needed to reduce fault current level of power systems and to satisfy the fault current constraints. The method employs a modified fault current constrained optimal power flow (FCC-OPF) with X variables for the candidate locations of splitting and for decision making on whether to split or not, it adopts soft-discretization by augmenting inversed U-shaped penalty terms. Also, this paper discusses the procedure on the adequate selection of bus splitting locations based on the results of the modified FCC-OPF, to reduce the total number of the actions taken.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.473-474
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• 2013

In this paper, a power flow control of PV hybrid module system with ESS is proposed. Photovoltaic(PV) hybrid module system is consist of individual converter, central inverter, and energy storage system(ESS). Because PV power can be changed in particular hours and environment condition, the power management control for ESS is required. In this paper, the power flow control method for PV hybrid module system with ESS is proposed. The validity of proposed control method is verified by simulations and theoretical analysis.

• KIEE International Transactions on Power Engineering
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• 제4A권4호
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• pp.192-200
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• 2004

This paper evaluates FACTS control on the available transfer capability (ATC) enhancement. Technical merits of FACTS technology on boosting ATC are analyzed. More effective control means for line flow and bus voltage require the application of FACTS. In this paper, the power flow calculation method for the power systems with FACTS is based on the current injection model (CIM) and the Newton-Raphson method. An integrated scheme for ATC calculation, which considers the dynamic characteristic of the power system, is suggested. The study is applied to the IEEE 57-bus power system to demonstrate the effectiveness of FACTS control on ATC enhancement.